Explosive assembly for restoring damaged casing

ABSTRACT

Disclosed herein is an explosive assembly for restoring collapsed or otherwise damaged oil well casing to its original shape. The assembly includes one or more elongated housings having shaped explosive charges within a carrier therefor and detonating components.

United States Patent Gillingham 51 May 22, 1973 EXPLOSIVE ASSEMBLY FOR References Cited RESTORING DAMAGED CASING UNITED STATES PATENTS [751 Ernest Lee Gillingham, Arlingmn 2,587,244 2 1952 Sweetman ..102/24 HC 2,758,543 8/1956 Grandin ..102/24 HC [73] Assignee: Jet Research Center, Inc., Arlington,

T Primary Examiner-Verlin R. Pendegrass Filed: y 1971 Attorney.lohn H. Tregomng, Thomas R. Weaver and Appl. No.: 166,160

US. Cl. ..102/20, 102/24 HC Int. Cl ..F42b 1/02 Field of Search ..102/20, 21.6, 21.8,

102/24 HC; l75/4.6

Michael J. Caddell 5 7 ABSTRACT Disclosed herein is an explosive assembly for restoring collapsed or otherwise damaged oil well casing to its original shape. The assembly includes one or more elongated housings having shaped explosive charges within a carrier therefor and detonating components.

9 Claims, 5 Drawing Figures PATENTED 2 3 SHEET 1 OF 2 FIGURE 10.

INVENTOR. Ernest L. GiHingham ATTOR FIGURE 1.

EXPLOSIVE ASSEMBLY FOR RESTORING DAMAGED CASING BACKGROUND OF THE INVENTION Oil and gas wells must be cased, among other reasons, to protect the well bore from loose formations which tend to crumble and would otherwise fall into and plug the well; from salt water producing formations; and to protect fresh water sands from being polluted by oil, gas and salt water. The casing used is generally heavy walled steel pipe which is cemented into the well bore.

Even though heavy walled steel pipe is used, formation pressures, sloughing formations, and other conditions can cause the collapse, bending, or other deformation of such pipe. These deformities can and do obstruct the passage of oil well tools and otherwise interfere with normal well operations. Under such conditions, it becomes necessary to remove or remedy such deformations.

The straightening or reforming of downhole casing can be effected using a number of tools known to the prior art. For example, rotary swages have been employed which restore the shape of the casing using pressure and rolling action. Other devices use hydraulic pressure to force a forming tool into the collapsed region of the casing.

However, a very efficient and quick method for remedying collapsed or bent casing downhole is by employing one or more elongated linear shaped charges to cut and expand the deformed casing back into its approximate original shape.

Accordingly, the present invention provides an explosive charge assembly for straightening collapsed or bent casing, which comprises a center support member, one or more elongated housing members having explosive means therein, means for attaching said housing members to said center support member, and means for detonating said explosive means.

BRIEF DESCRIPTION OF THE DRAWINGS An explosive charge assembly for straightening collapsed or bent casing, tubing and the like, constructed in accordance with a preferred embodiment of the invention is illustrated in the accompanying drawings in which:

FIG. 1 and 1a are side views of the preferred embodiment of the invention; and

FIG. 2 is a cross-sectional view taken along lines 2-2 of FIG. la;

FIGS. 3 and 4 illustrate the operation of the invention of FIG. 1 and la.

DESCRIPTION OF THE SPECIFIC EMBODIMENT Referring to the drawings and to FIG. 1 and 1a in particular, shown therein and generally designated by the reference character is the explosive charge assembly constructed in accordance with the invention. A cable head 11, located at the top of the drawing, connects assembly 10 to cable 12 on whicn the assembly 10 can be lowered into a well bore and also retrieved. An electrical conductor wire 13, shown emerging from cable head 11, is carried within cable 12 from a source of current on the surface (not shown).

A solid metal, elongated center support member 14, fastened at its upper end 16 to cable head 11 terminates at lower end 18.

Two identical rings, 20 and 22, are attached to member 14, one above the other; ring 20 is movable along member 14 while ring 22 is rigidly attached thereto. A plurality of narrow, flat spring steel bars, collectively numbered 24, are attached to rings 20 and 22 via bolts 26 which are received by threaded apertures (not shown) in the rings. Each bar 24 is attached to the ring in spaced relation one to the other; e.g., in the case of four bars on one ring, each bar would be spaced from its neighbor. From the point of attachment on rings 20 and 22, bars 24 extend outwardly and either upwardly or downwardly depending upon which ring the bar is attached. At a spaced interval from member 14, which interval can be varied as will be shown later, bars 24 assume a parallel direction relative to the carrier, such parallel portion designated at 28. Beyond portion 28, bar 24 forms a bow 30 having an apex 32 and an inwardly extending end 34.

A plurality of tubular housings, collectively num bered 36, having upper and lower ends 38 and 40 re spectively, are attached to metal bars 24 in parallel relation to member 14 as shown in FIG. 1. Each housing 36 is attached to one set of bars 24 where a set comprises two bars, one extending upwardly and the other extending downwardly, both bars being in the same vertical plane. The point of attachment is adjacent each end, 38 and 40 of housing 36, and the parallel portion 28 of bars 24, and is by means of conventional adjustable hose clamps collectively numbered 42.

The nature of housings 36 can best be explained by reference to FIG. 2, a cross-sectional view of one of the housings 36. As shown therein, housing 36 contains an explosive charge 44 confined as shown by a liner 46 which is shaped in the form of a V or other convex shape so that the energy created by the explosive charge will be focused into a high velocity jet moving in the direction shown by the arrow numbered 48. The empty space 50 within housing 36 provides a minimal optimal space in which the aforementioned jet can be formed.

Referring again to FIG. 1, a conventional detonator apparatus 52 is attached to member 14 adjacent upper end 16. Apparatus 52 contains a conventional electric blasting cap and booster, neither of which are shown. Current to activate the blasting cap is supplied via aforementioned cable 13. A plurality of primacords, collectively numbered 56, lead from a common attachment to the blasting cap within apparatus 52 to individual attachment with explosive charge 44 contained in each housings 36. The attachment of each primacord 56 to charges 44 via upper end 38 of housings 36 as well as all other components in assembly 10, are sealed to permit usage in fluid filled pressurized environments.

OPERATION OF THE SPECIFIC EMBODIMENT FIGS. 3 and 4 illustrate the operation of the invention described in FIGS. 1 and 2. In FIG. 3, there is shown a representative view of a well bore 60 lined with casing 62. A deformity in casing 62, shown at 64, is an obstruction to the passage of well tools to downhole locations. Explosive charge assembly 10 is prepared to remove deformity 64 by first selecting the number and appropriate sized housings 36 and attaching them to carrier 14 via metal bars 24. Ring 20 is then moved toward or away from ring 22 so that apexs 32 on bows 30 will define a diameter slightly greater than the internal diameter of casing 62. Ring 20 is then secured to member 14 to prevent slippage. Detonator assembly 52 is loaded with a blasting cap and primacords 56 are attached. Assembly can now be lowered, on cable 12, into the well bore. As the assembly travels downwardly the inwardly extending ends 34 of bows 30 on the downwardly extending bars 24 guide the assembly into casings of different sizes (if such are present) and past inwardly extending projections such as an upper end of a liner hanger (not shown). Passage through any such constrictions is easily accomplished by the capability of bars 24 flexing inwardly so as to permit the overall diameter of assembly 10 to be temporarily reduced. In addition to guiding assembly 10, bows 30, by extending outwardly further than housings 36, protect the housings from damaging contact with the walls of the casing through which the assembly travels.

After assembly 10 has been positioned adjacent deformity 64, as shown in FIG. 3, the blasting cap within detonator assembly 52 is fired, simultaneously igniting shaped charges 44 in housings 36 (see FIG. 2) via primacords 56. The result of such ignition is the formation ofjets of hot gases and minute particles of liner 46 which cut a vertical slot through casing 62 in front of each housing 36. One such slot is shown in FIG. 4, designated by reference character 66. In concert with and because of the cutting action of the jets, the explosive blast of charges 44 causes casing 62 to expand outwardly as shown in FIG. 4 and designated generally by reference character 68.

Following the firing of charge assembly 10, all components thereof, with the exception of the shattered housings 36, are withdrawn from well bore 60. Retrieval thereof is enhanced by the guiding action of upwardly extending bars 24 and the bows 30 and ends 34 thereon.

The slots 66 (in casing 62) can now be easily sealed via a number of different methods afterr which casing 62 is ready for normal use.

As is apparent to those skilled in the art, the instant invention has several very desirable and novel features. For example, the only debris resulting from the use of the invention is that from housings 36. Since the direction of the explosion is outwardly away from the assembly, the other components are relatively undamaged.

Another feature of the instant invention is that the number of linear charges can be varied as required. Instead of four as described above, any number may be employed, thus giving the explosive assembly the flexibility to meet the requirements of any particular situation.

Another feature resides in the flexible arrangement of housings 36 and bars 24.

Yet another feature of the instant invention resides in the ease in which it can be used; i.e., oilfield workers not skilled in the art can readily perform all the required steps with just simple instructions.

In constructing the various components of assembly 10, different materials are utilized. The center support member 14 is normally made from a heavy iron or steel to give weight and stability to the assembly. Bars 24 are made from a spring steel having flexibility coupled with a high memory retention. Housings 36 may be constructed from any number of strong, yet brittle materials such as ceramic, glass, or cast aluminum. The V- shaped framework 46 is preferably made from pressed powdered copper. The charge 44 may be any of the high explosives currently in use. Primacords 56 and the blasting cap are of conventional form and material as are the detonator assembly 52 and cable 13.

The instant invention has been described with reference to restoring collapsed or otherwise damaged casing positioned in an oil or gas well. However, the invention may be used in other situations. For example, it can be used in pipelines, in other buried horizontal conduits and in hollow vertical piers. Further, it may be used to quickly and economically cut elongated slots from within hollow bodies. Other uses for the instant invention will be readily apparent to those skilled in the art.

Although the invention has been described with reference to the embodiments illustrated, it will be apparent that many different embodiments may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

What is claimed is:

1. An explosive charge assembly for straightening collapsed or bent casing which comprises a center support member; a plurality of elongated housing members having explosive charges therein; means for flexible attachment of said housing members to and around said support member to permit flexible change in diameter of said explosive charge assembly, said housing members normally being spaced from and parallel to said support member; and detonating means for detonating said explosive charges.

2. The explosive charge assembly of claim 1 wherein said explosive charges are shaped charges.

3. The explosive charge assembly of claim 1 wherein said housing members are movably attached to said support member.

4. An explosive charge assembly for straightening collapsed or bent casing, which comprises an elongated, rigid center support member; an upper ring attached to said support member for slidable adjustment thereon; a lower ring fixedly attached to said support member below said upper ring; a plurality of housing members flexibly attached parallel to and at a distance from said support member by flexible attachment means, said flexible attachment means comprising a plurality of flexible upper members and a plurality of flexible lower members; said flexible upper members having one end of each fixed to said upper ring and the other end of each fixed to the upper end of one of said housing members and said flexible lower members having one end of each fixed to said lower ring and the other end of each fixed to the lower end of one of said housing members; said explosive charge assembly further comprising a plurality of elongated explosive shaped charges, each positioned in one of said housing members; and detonating means for detonating said shaped charges.

5. The explosive charge assembly of claim 4 having a cable head connected to the upper end of said center support member.

6. The explosive charge assembly of claim 4 wherein said flexible upper members and said flexible lower members are symmetrically arranged around said upper ring and said lower ring respectively.

7. The explosive charge assembly of claim 6 wherein each of said flexible upper members extend upwardly and outwardly from said upper ring and each of said flexible lower members extend downwardly and outwardly from said lower ring.

8. The explosive charge assembly of claim 4 wherein said distance between said housing members and said said flexible upper members and said flexible lower support members is adjustable by sliding said upper members are each narrow, flat spring steel bars. ring along said support member.

9. The explosive charge assembly of claim 4 wherein 

1. An explosive charge assembly for straightening collapsed or bent casing which comprises a center support member; a plurality of elongated housing members having explosive charges therein; means for flexible attachment of said housing members to and around said support member to permit flexible change in diameter of said explosive charge assembly, said housing members normally being spaced from and parallel to said support member; and detonating means for detonating said explosive charges.
 2. The explosive charge assembly of claim 1 wherein said explosive charges are shaped charges.
 3. The explosive charge assembly of claim 1 wherein said housing members are movably attached to said support member.
 4. An explosive charge assembly for straightening collapsed or bent casing, which comprises an elongated, rigid center support member; an upper ring attached to said support member for slidable adjustment thereon; a lower ring fixedly attached to said support member below said upper ring; a plurality of housing members flexibly attached parallel to and at a distance from said support member by flexible attachment means, said flexible attachment means comprising a plurality of flexible upper members and a plurality of flexible lower members; said flexible upper members having one end of each fixed to said upper ring and the other end of each fixed to the upper end of one of said housing members and said flexible lower members having one end of each fixed to said lower ring and the other end of each fixed to the lower end of one of said housing members; said explosive charge assembly further comprising a plurality of elongated explosive shaped charges, each positioned in one of said housing members; and detonating means for detonating said shaped charges.
 5. The explosive charge assembly of claim 4 having a cable head connected to the upper end of said center support member.
 6. The explosive charge assembly of claim 4 wherein said flexible upper members and said flexible lower members are symmetrically arranged around said upper ring and said lower ring respectively.
 7. The explosive charge assembly of claim 6 wherein each of said flexible upper members extend upwardly and outwardly from said upper ring and each of said flexible lower members extend downwardly and outwardly from said lower ring.
 8. The explosive charge assembly of claim 4 wherein said flexible upper members and said flexible lower members are each narrow, flat spring steel bars.
 9. The explosive charge assembly of claim 4 wherein said distance between said housing members and said support members is adjustable by sliding said upper ring along said support member. 